Method for reporting downstream packet resequencing status in cable modem

ABSTRACT

Provided is a method by which a cable modem reports a downstream packet resequencing status to a cable modem termination system, and more particularly, a method of effectively reporting detailed information on a packet resequencing status by further defining a packet resequencing-related event and event-related information in a message reporting the packet resequencing status. The method by which a cable modem reports a resequencing status of the resequenced packets includes the steps of: when a packet resequencing-related event occurs, generating a resequencing status message (CM-STATUS) including packet sequence numbers of packets causing the event; transmitting a band allocation request message for requesting a cable modem termination system to allocate an upstream band for transmission of the resequencing status message; and transmitting the resequencing status message to the cable modem termination system over the upstream band allocated by the band allocation request message. More detailed resequencing status information, such as the remaining capacity of the receive buffer and the resequenced packet map, for more packet resequencing-related events compared to the conventional downstream packet resequencing status reporting method, is transmitted to the CMTS, such that the CMTS copes more flexibly with situations that may occur upon packet resequencing.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean PatentApplication No. 2006-122022, filed Dec. 5, 2006, and No. 2007-50778,filed May 25, 2007, the disclosure of which is incorporated herein byreference in its entirety.

BACKGROUND

1. Field of the Invention

The present invention relates to a method by which a cable modem (“CM”)reports a downstream packet resequencing status to a cable modemtermination system (“CMTS”), and more particularly, to a method ofeffectively reporting detailed information on a packet resequencingstatus by further defining a packet resequencing-related event andevent-related information in a message reporting the packet resequencingstatus.

The present invention has been produced from the work supported by theIT R&D program of MIC (Ministry of Information and Communication)/IITA(Institute for Information Technology Advancement) [2006-S-019-01, TheDevelopment of Digital Cable Transmission and Receive System for 1 GbpsDownstream] in Korea.

2. Discussion of Related Art

In general, a cable modem network attracts attention together with anintegrated services digital network (ISDN), a multi digital subscriberline (xDSL), and the like in the field of remote connections. The cablemodem network provides a variety of services, such as working from home,video conferencing, web surfing and the like, to subscribers at a highdata rate on the order of Mbps in connection with the Internet or anIntranet.

A cable modem network is widely used in the U.S. and may be based upon acable television (CATV) network for data communications. The cable modemnetwork is similar to the CATV network in that it uses a coaxial cable.However, in the CATV network, an external coaxial cable is connected toa set top box, which is then connected with a television (TV), and inthe cable modem network, a cable modem is used to connect a coaxialcable with a personal computer (PC). In this case, one or more PCs maybe connected to the cable modem.

Referring to FIG. 1, a cable network may include a cable modem (CM) 120for allowing a user to transmit and receive data, and a cable modemtermination system (CMTS) 110 connected to a wide area network fortransmitting and receiving data to and from the user. The CMTS 110 islocated at a headend and receives data from the CM 120 at home(upstream), and transmits data to the CM 120 (downstream).

The transmission of data packets from the CMTS 110 to the CM 120 may bemade by a plurality of downstream channels (DC) rather than one channel.The CM 120 may resequence, in an original order, the packets receivedover the different channels.

FIG. 2 illustrates a cable modem network in which data transmission andreception is made over a plurality of downstream channels.

Referring to FIG. 2, the CMTS 210 receives packets from a network-sideinterface (NSI) 240. In the CMTS 210, a classifier 211 classifies thereceived packets into common packets 215 and resequenced packets 216.

The common packets 215 are directly delivered to a scheduler 213 of theCMTS 210 and then to the CM 220 via one downstream channel 214.

On the other hand, the resequenced packets 216 are first delivered to asequencer/distributor 212 before being provided to the scheduler. Thesequencer sequentially allocates a sequence number to the respectiveresequenced packets 216, and the distributor distributes the packets tothe respective schedulers 213 according to a predetermined rule.

Each channel scheduler 213 of the CMTS 210 transmits the received packetover the downstream channel 214 according to a scheduler algorithm.

The CM 220 processes the packets received over the plurality ofdownstream channels 214 and transmits the packets to customer premiseequipment (CPE).

In this way, the CM 220 receives the common packets from the singlechannel and the resequenced packets from the plurality of channels.Since the resequenced packets are distributed by the CMTS 210 to theplurality of channels, the received packets at the CM 220 may differ insequence from the packets input from the network-side interface 240 tothe CMTS 210 depending on settings of the schedulers and the downstreamchannels. In order to transmit the packets to the customer premiseequipment in the same sequence input from the network-side interface 240to the CMTS 210, the CM 220 may perform a packet resequencing processusing information received from the CMTS 210 and information included inthe packets.

In an initialization process, the CMTS 210 transmits a downstreamservice ID (“DSID”) to the CM 220, so that the packet resequencingprocess is performed. The CMTS 210 then includes the DSID together witha packet sequence number (“PSN”) for resequencing in the resequencedpackets and transmits the resultant resequenced packets to the CM 200.The CM 220 may perform the packet resequencing process based on suchinformation.

FIG. 3 illustrates a format of the resequenced packet transmitted fromthe CMTS to the CM.

Referring to FIG. 3, the resequenced packet includes a MAC header 310and MAC data 320.

The MAC header includes a frame control (FC) field 311 indicating a typeof a frame and the presence of an extended header (EHDR), a MACparameter field (MAC_PARM) 312 indicating a length of the EHDR, a lengthfield (LEN) 313 indicating a total length of the frame, a header checksequence (HCS) field 314 for error check of the MAC header 310, and theEHDR 315 having packet resequencing information and output priorityinformation. The EHDR 315 includes a 4-bit EHDR type field EH_Type, a4-bit length field EH_LEN, a 3-bit traffic priority field, a 1-bitsequence change counter (“SCC”) field, a 20-bit DSID field, and a 16-bitPSN field.

FIGS. 4 a and 4 b illustrate a format of a MAC domain description (MDD)message transmitted from the CMTS to the CM, and a type/length/value(TLV) format, respectively. The MDD message is periodically transmittedfrom the CMTS to the CM over each downstream channel, and mainly used bythe CM in an initialization process for transmission between the CMTSand the CM.

Referring to FIG. 4 a, the MDD message, which is transmitted from theCMTS to the CM over a primary downstream channel, includes a MACmanagement header 410, fixed fields 420, and TLV encoding information430 containing MAC domain information.

FIG. 4 b illustrates a TLV format related to the control of transmissionof a CM-STATUS message in the TLV encoding information 430 for reportinga resequenced packet status from the CM to the CMTS. Among sub TLVs of adownstream active channel list TLV 440 represented by Type=1, aCM-STATUS event enable bitmask TLV 442 of Type=1.5 (indicating that theCM-STATUS event enable bitmask TLV 442 is a sub TLV of Type=1 and has atype of 5) and a CM-STATUS event control TLV 460 represented by Type=11describe information for controlling the transmission of the CM-STATUSmessage.

The CM-STATUS event enable bitmask TLV 442 consists of a 2-byte bitmask.For example, the DOCSIS 3.0 standard defines a fourth bit as asequence-out-of-range event. The sequence-out-of-range event refers toan event occurring when resequenced packets cannot be stored in areceive buffer due to the limited capacity of the receive buffer.

Where the fourth bit is set to 1, the CM is required to transmit theCM-STATUS message when there is a sequence-out-of-range packet in theresequenced packets received over a downstream channel with a downstreamchannel ID (“DCID”) indicated by the channel ID TLV 441 a. If the fourthbit is 0, the CM does not transmit the CM-STATUS message even if thereis the sequence-out-of-range packet.

The CM-STATUS event control TLV 460 includes sub TLVs, such as an eventtype code TLV 461 of type=11.1, a maximum event hold-off timer TLV 462of type=11.2, and a maximum number of reports-per-event TLV 463 oftype=11.3.

In an exemplary embodiment, the DOCSIS 3.0 standard defines that theevent type code value of the sequence-out-of-range event is 3. When theevent type code TLV 461 value in the MDD message is 3 and asequence-out-of-range event occurs, the CM is required to performCM-STATUS message transmission according to a process shown in FIG. 7 byusing the maximum event hold-off timer TLV 462 value and the maximumnumber of reports-per-event TLV 463 value.

FIGS. 5 a and 5 b illustrate a format of a multipart registrationresponse (REG-RSP-MP) message transmitted from the CMTS to the CM, and aTLV format, respectively. The REG-RSP-MP message is a message that theCMTS transmits to the CM in response to a registration request message(REG-REQ-MP) from the CM. The REG-RSP-MP message is used forregistration of information required for the transmission between theCMTS and the CM.

Referring to FIG. 5 a, the REG-RSP-MP message includes a MAC managementheader 505, fixed fields 510, and TLV encoding information 515containing registration information.

FIG. 5 b illustrates a format of a DSID encoding TLV in TLV information515 forming the REG-RSP-MP message. The DSID encoding TLV 520represented by Type=50 includes: sub TLVs, such as a DSID TLV 525 oftype=50.1 indicating a DSID value; a DSID action TLV 530 of type=50.2indicating addition, deletion or change of the DSID indicated in theDSID TLV 525; and a downstream resequencing encoding TLV 535 oftype=50.3 describing whether resequencing is required and additiveparameter information required for resequencing.

The downstream resequencing encoding TLV 535 includes sub TLVs. That is,the downstream resequencing encoding TLV 535 includes a resequencingDSID indication TLV 540 of type=50.3.1 indicating whether resequencingis required. In the case where resequencing is required, the downstreamresequencing encoding TLV 535 further includes, as parameterinformation: a resequencing channel list TLV 545 indicating channelsover which downstream packets with the DSID TLV 525 value can betransferred; a resequencing wait time TLV 550 of type=50.3.3; aresequencing warning threshold TLV 555 of type=50.3.4; and a CM-STATUSmaximum event hold-off timer TLV 560 of type=50.3.5 forsequence-out-of-range events.

The maximum event hold-off timer TLV 462 of the MDD message is replacedwith the CM-STATUS maximum event hold-off timer TLV 560.

FIGS. 6 a and 6 b illustrate a format of a CM control request(CM-CTRL-REQ) message transmitted from a CMTS to a CM in order toinstruct to perform a specific activity and a TLV format, respectively.

Referring to FIG. 6 a, the CM-CTRL-REQ message includes a MAC managementmessage header 610, a fixed transaction ID field 620, and a TLV encodinginformation field 630.

FIG. 6 b illustrates a format of a downstream status event enablebitmask override TLV related to transmission of the CM-STATUS message inTLV encoding information 630 of the CM-CTRL-REQ message. The downstreamstatus event enable bitmask override TLV 640 represented by Type=5includes sub TLVs, such as a DCID TLV 650 of type=5.1, and a downstreamstatus event enable bitmask TLV 660 of type=5.2. The CM-STATUS eventenable bitmask TLV 442 may be replaced with the downstream status eventenable bitmask TLV 660.

In response to receipt of the CM-CTRL-REQ message, the CM is required torespond to the CMTS with a CM-CTRL-RSP message, which has the sameformat as the CM-CTRL-REQ message format as shown in FIG. 6 a.

FIG. 7 illustrates a CM-STATUS event type state machine running on theCM. The CM-STATUS event type state machine is a kind of finite statemachine (FSM) for determining, based on event-based state transition ofthe CM, whether the CM transmits a CM-STATUS message includingresequenced packet status information.

Referring to FIG. 7, the CM operates the CM-STATUS event type statemachine consisting of an IDLE 705 state and a SENDING 725 state forrespective events allowing for transmission of the CM-STATUS message viaan MDD message or a CM-CTRL-REQ message.

In the IDLE state 705, the CM has the transaction ID (TID) value ofzero. When a state transitions from the IDLE state to an “on” state dueto occurrence of an event of a specific type (710), the CM sets aReportsLeft variable to a maximum number of reports defined for theevent and a FirstReport control variable to True (715). The CM thenselects any one value between 0 and the maximum hold-off value definedfor the event and uses it as an initial reporting hold-off timer (720).The CM then transitions to a SENDING state and is kept in the SENDINGstate while the defined timer is operating (725).

Upon expiration of the hold-off timer in the SENDING state 725 (730),the CM determines whether the event type is kept in the “on” state(735). If the event is changed to an “off” state, the CM transitions tothe IDLE state (705) instead of transmitting the CM-STATUS message.

If the event is kept in the “on” state, the CM determines whether atransmission of the CM-STATUS message is the first time(FirstReport=True) (740). If the transmission is the first time, the CMsets the FirstReport control variable to False and increments the TIDvalue by one. The TID value can increase to 255 and then is reset to one(wraparound). If the FirstReport control variable value is False, the CMmaintains the TID value unchanged.

The CM transmits the CM-STATUS message (745). The CM then determineswhether the ReportsLeft variable value is zero (750). The zero meansthat the CM should transmit the CM-STATUS message unlimitedly until theevent becomes “off”. If the ReportsLeft value is not zero, the CMdecrements the ReportsLeft value by one.

When the ReportsLeft variable value decrements from one to zero, the CMtransitions to the IDLE state (705) in step 755. When the ReportsLeftvariable value does not decrement from one to zero, the CM sets thehold-off timer to the maximum hold-off value (760).

Where the event of the relevant type is released and then regeneratedprior to the expiration of the hold-off timer in the SENDING state 725in step 765, the CM sets the ReportsLeft variable to a maximum reportsvalue defined for the event again and sets the FirstReport controlvariable to True (770). Step 770 is the same as step 715, except thatthe SENDING state is maintained directly without step 720.

If the hold-off timer value for the event type is changed by the MDDmessage prior to the expiration of the hold-off timer in the SENDINGstate 725 in step 775, the CM proceeds to step 720.

If the transmission of the CM-STATUS message for the event typegeneration by the MDD message or CM-CTRL-REQ message is prohibited priorto the expiration of the hold-off timer in the SENDING state 725 in step780, the CM transitions to the IDLE state (705) instead of transmittingthe CM-STATUS message.

FIGS. 8 a and 8 b illustrate a format of a CM-STATUS message transmittedfrom the CM to the CMTS, and a TLV format, respectively. Here, theCM-STATUS message is a message that the CM transmits to report aresequencing status to the CMTS when a resequencing-related event occursat the CM.

Referring to FIG. 8 a, the CM-STATUS message includes a MAC managementmessage header 810, a fixed transaction ID field 820, and a TLV encodinginformation field 830.

FIG. 8 b illustrates a TLV format of event information causingtransmission of the CM-STATUS message in the TLV encoding information830 of the CM-STATUS message. The status event TLV 840 represented byType=1 includes sub TLVs, such as an event type code TLV 845 oftype=1.1, an event description TLV 850 of type=1.2 describing details ofan event, a transaction ID TLV 855 of type=1.3, a downstream channel IDTLV 860 of type=1.4, an upstream channel ID TLV 865 of type=1.5, and aDSID TLV 870 of type=1.6.

In an exemplary embodiment, when a sequence-out-of-range event occurs atthe CM and reporting a status of the sequence-out-of-range event via theMDD message or the CM-CTRL-REQ message is allowed, the CM generates theCM-STATUS message to the CMTS, which includes the event type code TLV845 value set to 3, the transaction ID TLV 855 value set to a propervalue, and the DSID TLV 870 value set to a DSID value to which a packetwith an event belongs.

In the conventional cable network using the packets and messages of theformat as described above, via the CM-STATUS message the CM notified theCMTS of only a sequence-out-of-range event among several eventsoccurring upon receipt of the resequenced packets from the CMTS. In thiscase, only DSID information of a packet causing the event is notifiedvia the CM-STATUS message. This allows the CMTS to only delete thepacket causing the event by use of the information.

Moreover, the CM-STATUS message is not transmitted immediately after theevent occurs. That is, the CM-STATUS message is not transmitted untilthe band is allocated in response to a queue-depth based resourcerequest (“QD-REQ”) message competitively transmitted for transmission ofthe CM-STATUS message generated at the time of expiration of thehold-off timer driven by the CM.

According to the reporting scheme used in the conventional cablenetwork, the CM cannot rapidly report accurate information on varioussituations occurring upon the receipt of the resequenced packets to theCMTS. Furthermore, since the CMTS can receive the resequencing statusinformation if, and only if, an event is generated from the CM, itcannot cope with problematic situations flexibly. In particular, in a CMcomprising a receive buffer having limited capacity, a packet loss maybe frequently caused by receive buffer overflow.

SUMMARY OF THE INVENTION

The present invention is directed to a method by which a CM rapidlyreports to a CMTS more detailed information on several situationsoccurring in a packet resequencing process.

The present invention is also directed to a method for periodicallyreporting a remaining capacity of a receive buffer to a CMTS andreporting information on resequenced packets stored in the receivebuffer to minimize a packet loss due to overflow in the receive buffer.

The present invention is also directed to a method by which a CMTSrequests resequencing status information from a CM and the CM reportsthe resequencing status information in response to the request.

The present invention is also directed to a method for allocating anupstream band so that resequencing status information from a CM israpidly reported.

One aspect of the present invention provides a method by which a cablemodem reports a resequencing status of resequenced packets, the methodcomprising the steps of: when a packet resequencing-related eventoccurs, generating a resequencing status message (CM-STATUS) includingpacket sequence numbers of packets causing the event; transmitting aband allocation request message for requesting a cable modem terminationsystem to allocate an upstream band for transmission of the resequencingstatus message; and transmitting the resequencing status message to thecable modem termination system over the upstream band allocated by theband allocation request message. Preferably, the event may comprise arapid loss detection event.

Another aspect of the present invention provides a method by which acable modem reports a resequencing status of resequenced packets, themethod comprising the steps of: generating a resequencing status messageat the cable modem in a predetermined period; allocating to the cablemodem, by a cable modem termination system, an upstream band fortransmission of the resequencing status message in the predeterminedperiod; and transmitting the resequencing status message to the cablemodem termination system over the allocated upstream band. Preferably,the allocating step may comprise allocating the upstream band by using aservice ID for periodic reporting.

Still another aspect of the present invention provides a method by whicha cable modem receiving resequenced packets over a plurality of channelsreports a resequencing status of the resequenced packets, the methodcomprising the steps of: receiving a request message (CM-CTRL-REQ) froma cable modem termination system, the request message requesting thecable modem to report the resequencing status; generating a responsemessage (CM-CTRL-RSP) in response to the request message; allocating tothe cable modem, by the cable modem termination system, an upstream bandfor transmission of the response message; and transmitting the responsemessage to the cable modem termination system over the allocatedupstream band. Preferably, the request message may comprise upstreamband allocation information for transmission of the response message,and the allocating step may comprise allocating the upstream band byusing the upstream band allocation information.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present inventionwill become more apparent to those of ordinary skill in the art bydescribing in detail preferred exemplary embodiments thereof withreference to the attached drawings in which:

FIG. 1 is a block diagram of a typical cable modem network;

FIG. 2 illustrates a cable modem network in which data transmission andreception is made over a plurality of downstream channels;

FIG. 3 illustrates a format of a resequenced packet transmitted from acable modem termination system (CMTS) to a cable modem (CM);

FIGS. 4 a and 4 b illustrate a format of a MDD MAC domain descriptionmessage transmitted from the CMTS to the CM, and a type/length/value(TLV) format, respectively;

FIGS. 5 a and 5 b illustrate a format of a multipart registrationresponse (REG-RSP-MP) message transmitted from a CMTS to a CM, and a TLVformat, respectively;

FIGS. 6 a and 6 b illustrate a format of a CM control request(CM-CTRL-REQ) message transmitted from a CMTS to a CM in order toinstruct to perform a specific activity, and a TLV format, respectively;

FIG. 7 illustrates a CM-STATUS event type state machine running on a CM;

FIGS. 8 a and 8 b illustrate a format of a CM-STATUS message transmittedfrom a CM to a CMTS, and a TLV format, respectively;

FIG. 9 illustrates a DSID encoding-related TLV format of an REG-RSP-MPmessage according to an exemplary embodiment of the present invention;

FIG. 10 illustrates a TLV format of a CM-STATUS message according to anexemplary embodiment of the present invention;

FIG. 11 illustrates a process of transmitting a CM-STATUS messageaccording to an exemplary embodiment of the present invention;

FIG. 12 illustrates a TLV format of a CM-CTRL-REQ message according toan exemplary embodiment of the present invention;

FIG. 13 illustrates a format of an additive TLV of a CM-CTRL-RSP messageaccording to an exemplary embodiment of the present invention; and

FIG. 14 illustrates a process of exchanging a CM-CTRL-REQ message and aCM-CTRL-RSP message according to an exemplary embodiment of the presentinvention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, exemplary embodiments of the present invention will bedescribed in detail. However, the present invention is not limited tothe exemplary embodiments disclosed below, but can be implemented invarious forms. Therefore, the following exemplary embodiments aredescribed in order for this disclosure to be complete and enabling tothose of ordinary skill in the art.

FIG. 9 illustrates a DSID encoding-related TLV format of an REG-RSP-MPmessage according to an exemplary embodiment of the present invention.

In the REG-RSP-MP message according to an exemplary embodiment of thepresent invention, packet resequencing-related events causingtransmission of a CM-STATUS message may be further defined in adownstream resequencing encoding TLV 535 of type=50.3. A TLV format fordescribing parameters of the events may be added.

As one of the added events, there is an event for allowing the CM totransmit a CM-STATUS message when rapid loss detection is generated forresequenced packets with the same DSID. The rapid loss detection refersto the CM rapidly detecting that a packet with a specific PSN is lost,from the result of receiving packets over a plurality of downstreamchannels.

As another added event, there is a timeout event of packets stored inthe resequencing process. Where any received resequenced packets arestored in the receive buffer for resequencing, the CM stores the packetsonly for a predetermined time in consideration of the limited capacityof the receive buffer. The stored packets may not be resequenced evenafter the predetermined time expires. This is called a resequencingpacket timeout.

Finally, a periodic resequencing status reporting event may be added,which periodically reports the resequenced packet status.

The added events may be provided with a type code value capable ofidentifying an event from the event type code TLV 461 or 845 and with abit location capable of identifying an event from the event enablebitmask TLV 442 or 660.

Referring to FIG. 9, the REG-RSP-MP message includes sub TLVsconstituting a DSID encoding TLV 905 extended from the conventional DSIDencoding TLV 520 to further define parameters related to the CM-STATUSmessage transmission for the added events. The sub TLVs include: a2-byte CM-STATUS maximum event hold-off timer TLV 910 of type=50.3.6 forrapid loss detection events, which is applied upon occurrence of a rapidloss detection event; a 2-byte reporting period TLV 920 of type=50.3.7for indicating a reporting period of a periodic resequencing statusreporting event; and a 2-byte CM-STATUS maximum event hold-off timer TLV940 of type=50.3.9 for a resequencing packet timeout event, which isapplied upon occurrence of the resequencing packet timeout event.

Also, the CMTS may allocate a periodic band for CM-STATUS messagetransmission for a periodic status reporting event. The CMTS notifiesthe CM of the band allocation. To define a service ID for periodicresequencing status reporting (“R_SID”) used upon the periodic bandallocation, a SID TLV 930 for periodic resequencing reporting is furtherdefined.

FIG. 10 illustrates a TLV format of a CM-STATUS message according to anexemplary embodiment of the present invention.

Referring to FIG. 10, the CM-STATUS message may have a status event TLV1010 extended from the conventional status event TLV 840 and defined toinclude detailed resequencing status information. The extended statusevent TLV 1010 may include a sequence-out-of-range PSN list TLV 1020, arapid loss detection event PSN list TLV 1030, a timeout PSN list TLV1040, and a stored resequenced packet map TLV 1050. Thesequence-out-of-range PSN list TLV 1020, the rapid loss detection eventPSN list TLV 1030, and the timeout PSN list TLV 1040 are necessarilyincluded upon occurrence of respective events and describe PSN values ofthe resequenced packets which cause the events, in a list form.

The stored resequenced packet map TLV 1050 is necessarily included uponoccurrence of a periodic resequencing status reporting event. The storedresequenced packet map TLV 1050 may include a 4-byte remaining bufferwindow field 1051, a 2-byte next expected PSN field (“NEPSN”) 1052, a2-byte earliest PSN field 1053 for stored resequenced packets, and abitmap field 1054 for the stored packets.

When the CM operates the receive buffer independently for each DSID, theremaining buffer window field 1051 may indicate a remaining window of acorresponding DSID receive buffer. The remaining buffer window field1051 may indicate a remaining window of a packet buffer pool when the CMoperates the receiver buffer as a packet buffer pool for all DSIDs.

Referring to FIG. 10, since a length field value of the storedresequenced packet map TLV 1050 is n, the bitmap field 1054 for thestored packets has a length of (n−8) bytes, i.e., (n−8)×8 bits as aresult of subtraction of a sum of lengths of the other fields, 8, fromn. In the stored packet bitmap field 1054, a first bit indicates whetherthere is a packet having a PSN greater by one than N+a, which is the PSNminimum value 1053 of the stored resequenced packets, and a last bitindicates whether there is a packet having a PSN greater by (n−8)×8 thanN+a.

FIG. 11 illustrates a process of transmitting the CM-STATUS messageaccording to an exemplary embodiment of the present invention.

For initialization, the CMTS 1120 transmits the extended DSID encodingTLV 905 information via the REG-RSP-MP message to the CM 1110 andregisters DSID and resequencing related event reporting information(1130).

After the initialization process is completed, the CMTS 1120 begins totransmit resequenced packets to the CM 1110 and drives a timer forperiodic resequencing status reporting (1140). During the transmissionby the CMTS 1120 of the resequenced packets, the timer expires in apredetermined period (1145 a to 1145 c). Upon each expiration of thetimer, the CMTS 1120 automatically allocates an upstream channel bandfor CM-STATUS message transmission to the CM 1110 even without aseparate request (1150 a to 1150 c). The upstream channel bandallocation may be performed by using R_SID.

The CM 1110, after allocated the band, transmits a CM-STATUS messageincluding the stored resequenced packet map TLV 1050 to the CMTS 1120(1160 a to 11160 c).

If, during the reception by the CM 1110 of the resequenced packets, oneof the sequence-out-of-range event, the rapid loss detection event orthe resequencing packet timeout event occurs (1165), the CM performshold-off using the hold-off timer value defined for each event andgenerates the CM-STATUS message. After generating the CM-STATUS message,the CM 1110 requests an upstream band resource by using the QD-REQmessage for transmission of the CM-STATUS message (1170).

After receiving the QD-REQ message 1170, the CMTS 1120 allocates theresource for transmission of the CM-STATUS message (1180), and the CM1110 transmits the CM-STATUS message containing the event-related TLV(1190). In this case, the CM-STATUS message may optionally include astored resequenced packet map TLV 1050.

In an exemplary embodiment, upon receipt of the resequencing statusinformation fed back from the CM, the CMTS may adjust a transmissionrate for the resequenced packets so that the packets are lost. When thepackets are lost, the CMTS may perform packet re-transmission.

FIG. 12 illustrates a TLV format of a CM-CTRL-REQ message according toan exemplary embodiment of the present invention.

Referring to FIG. 12, the CM-CTRL-REQ message may further include arequest TLV 1210 represented by Type=7 and defined to instruct the CM toimmediately report resequenced packet status information.

The request TLV 1210 for immediately reporting the resequenced packetstatus information may include sub TLVs, such as a 3-byte DSID TLV 1220of type=7.1 for immediate resequencing-status reporting, and a 12-byteimmediate reporting method TLV 1230 of type=7.2.

The DSID TLV 1220 for immediate resequencing-status reporting indicatesDSIDs of packets requested for resequenced packet status reporting, andthe immediate reporting method TLV 1230 describes a method by which theCM transmits the CM-CTRL-RSP message in response to the CM-CTRL-REQmessage.

In an exemplary embodiment, the CMTS may allocate a band for CM-CTRL-RSPmessage transmission to the CM by using the CM-CTRL-REQ message. To thisend, the immediate reporting method TLV 1230 may include sub TLVs, suchas a 1-byte upstream channel ID (“UCID”) TLV 1240 of type=7.2.1, a3-byte band allocation start time (“AllocStartTime”) TLV 1150 oftype=7.2.2, and a 2-byte band allocation duration TLV 1160 oftype=7.2.3.

FIG. 13 illustrates a format of an additive TLV of the CM-CTRL-RSPmessage according to an exemplary embodiment of the present invention.

In an exemplary embodiment, upon receipt of the CM-CTRL-REQ messagecontaining the request TLV 1210 for immediately reporting resequencedpacket status information, the CM immediately reports to the CMTS astored state of the resequenced packets having a DSID of the DSID TLV1220 for immediate resequencing-status reporting by means of theCM-CTRL-RSP message.

The CM-CTRL-RSP message for reporting may include a 3-byte DSID TLV 1310of Type=8 for immediate resequencing-status reporting that has the samevalue as the DSID TLV 1220 for immediate resequencing-status reportingincluded in the CM-CTRL-REQ message, and a stored resequenced packet mapTLV 1320 of Type=9 that has a variable length. Referring to FIG. 13, thestored resequenced packet map TLV 1320 may include a remaining bufferwindow field 1321, an NEPSN field 1322, an earliest PSN field 1323 forstored resequenced packets, and a bitmap field 1324 for stored packets,like the stored resequenced packet map TLV 1050 shown in FIG. 10.

FIG. 14 illustrates a process of exchanging the CM-CTRL-REQ message andthe CM-CTRL-RSP message according to an exemplary embodiment of thepresent invention.

For initialization, the CMTS 1420 transmits the extended DSID encodingTLV 905 information via the REG-RSP-MP message to the CM 1410 andregisters the DSID and resequencing related event reporting information(1430). Following the initialization, during the transmission of theresequenced packet to the CM 1410 (1440), the CMTS 1420 may transmit, tothe CM, a CM-CTRL-REQ message containing a request TLV 1210 of Type=7for immediately reporting resequenced packet status information (1450).

Upon receipt of the CM-CTRL-REQ message, the CM 1410 first recognizesthe DSID TLV 1220 of Type=7.1 for immediate resequencing-statusreporting and generates a CM-CTRL-RSP message containing the DSID TLV1310 of Type=8 for immediate resequencing-status reporting and thestored resequenced packet map TLV 1320 of Type=9. Using the bandresource allocated via the immediate reporting method TLV 1230 ofType=7.2 in the CM-CTRL-REQ message received from the CMTS 1420 (1451),the CM 1410 transmits the generated CM-CTRL-RSP message to the CMTS 1420(1452).

Alternatively, the CMTS 1420 may transmit the CM-CTRL-REQ messagewithout the immediate reporting method TLV 1230 of Type=7.2 to the CM1410 (1460). In this case, since further band allocation is required forCM-CTRL-RSP message transmission, the CM 1410 transmits a QD-REQ messagefor band allocation to the CMTS 1420 in step 1461. The CM is thenallocated the band resource from the CMTS (1462). The CM 1410 transmitsthe CM-CTRL-RSP message by using the allocated band resource (1463).

According to the present invention, more detailed resequencing statusinformation, such as the remaining capacity of the receive buffer andthe resequenced packet map, for more packet resequencing-related eventscompared to the conventional downstream packet resequencing statusreporting method is transmitted to the CMTS, such that the CMTS copesmore flexibly with situations that may occur upon packet resequencing.

Further, the resequencing status is reported upon event occurrence, aswell as in a predetermined period and upon a CMTS's request, which maybe selected according to a policy of the CMTS.

Furthermore, the upstream band for resequencing status reportingperformed periodically or in response to the CMTS's request is allocatedin advance without the request from the CM, thereby improving rapidityof the reporting and conserving resources.

While the invention has been shown and described with reference tocertain exemplary embodiments thereof, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims.

1. A method by which a cable modem receiving resequenced packets over aplurality of channels reports a resequencing status of the resequencedpackets, the method comprising the steps of: (a) when a packetresequencing-related event occurs, generating a resequencing statusmessage (CM-STATUS) in which packet sequence numbers (PSN) of theresequenced packets causing the event are recorded on a field designatedfor the event, the resequencing status message including asequence-out-of-range PSN list TLV, a rapid loss detection event PSNlist TLV, and a timeout PSN list TLV, wherein the resequencing statusmessage comprises a map of the resequenced packets stored in the cablemodem, the map of the stored resequenced packets comprises at least oneof a remaining window of a receive buffer of the cable modem, a nextexpected packet sequence number, an earliest packet sequence number ofthe stored resequenced packets, and a stored packet bitmap; (b)transmitting a band allocation request message for requesting a cablemodem termination system to allocate an upstream band for transmissionof the resequencing status message; and (c) transmitting theresequencing status message to the cable modem termination system overthe upstream band allocated by the band allocation request message. 2.The method of claim 1, wherein the event comprises a rapid lossdetection event.
 3. The method of claim 1, wherein the event furthercomprises a resequencing packet timeout event occurring at a receivebuffer of the cable modem.
 4. A method by which a cable modem receivingresequenced packets over a plurality of channels reports a resequencingstatus of the resequenced packets, the method comprising the steps of:(a) generating a resequencing status message at the cable modem in apredetermined period, wherein the resequencing status message includes amap of the resequenced packets stored in the cable modem, the map of theresequenced packets includes a remaining window of a receive buffer ofthe cable modem, an earliest packet sequence number of the storedresequenced packets, a next expected packet sequence number and a storedpacket bitmap; (b) allocating to the cable modem, by a cable modemtermination system, an upstream band for transmission of theresequencing status message in the predetermined period; and (c)transmitting the resequencing status message to the cable modemtermination system over the allocated upstream band.
 5. The method ofclaim 4, wherein step (b) comprises allocating the upstream band using aservice ID for periodic reporting.
 6. A method by which a cable modemreceiving resequenced packets over a plurality of channels reports aresequencing status of the resequenced packets, the method comprisingthe steps of: (a) receiving a request message (CM-CTRL-REQ) from a cablemodem termination system, the request message requesting the cable modemto report the resequencing status, the request message comprisingupstream band allocation information for transmission of a responsemessage, the upstream band allocation information including an upstreamchannel ID (UCID), a band allocation start time, and a band allocationduration; (b) generating the response message (CM-CTRL-RSP) in responseto the request message, wherein the response message comprises a map ofthe resequenced packets stored in the cable modem, wherein the map ofthe resequenced packets stored in the cable modem comprises a remainingwindow of a receive buffer of the cable modem, a next expected packetsequence number, an earliest packet sequence number of the storedresequenced packets, and a stored packet bitmap; (c) allocating to thecable modem, by the cable modem termination system, an upstream band fortransmission of the response message; and (d) transmitting the responsemessage to the cable modem termination system over the allocatedupstream band.
 7. The method of claim 6, wherein step (c) comprisesallocating the upstream band by using the upstream band allocationinformation.
 8. The method of claim 6, further comprising, before step(c), the step of transmitting a band allocation request message forrequesting the cable modem termination system to allocate the upstreamband for transmission of the response message.